Patterns of assimilate distribution in soybeans at maturity. III.* The contribution of assimilate to pods near the apex in determinate types

Abstract

The distribution of ¹⁴C from leaves to pods at upper nodes in indeterminate soybeans was examined in two breeding lines. In one, each node carried pods, but the highest node had no leaf. In the other there were leaves at each node, but the second node from the top had no pods. Leaves were supplied with ¹⁴CO₂ at each of the upper nodes, at a series of developmental stages from pod set to maturity, and the ¹⁴C distribution between the pods at the various nodes was determined at maturity. In both of the lines, acropetal movement to racemes became increasingly important towards the top of the plant. The higher racemes, which did not have the relationships with leaves above them or at the same level that those lower in the canopy had, drew assimilates from lower leaves. The only major differences between the patterns of distribution related to the missing raceme. The duration of pod-filling and the retention of photosynthetic capacity at the upper nodes appeared to be important for seed growth in the pods at those positions.

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*Part II, Aust. J. Agric. Res., 28: 395 (1977).